This invention relates to the extraction of hydrocarbon products from oil shale. More specifically, this invention relates to the cooling, depressurizing and moisturizing of retorted oil shale particles produced in a retorting process operated at superatmospheric pressure.
In a superatmospheric pressure retorting process, such as described in U.S. Pat. No. 3,361,644, crushed oil shale particles are passed through a retort wherein the particles are heated to between 800.degree. and 1,100.degree. F., typically by a countercurrently flowing stream of hot eduction gas. At these high temperatures most of the hydrocarbonaceous material within the oil shale decomposes into lighter, petroleum-like material and flows to a collecting zone where it is drawn off as shale oil and product gas. The retorting process is preferably carried out at superatmospheric pressures, typically between 10 and 50 p.s.i.g., to reduce the volume of recycled eduction gas necessary to provide the 350,000 to 450,000 Btu's per ton of oil shale typically required by the process. Retorting at superatmospheric pressures however raises the problem of how to remove processed (retorted) oil shale particles from the hot, pressurized retorting atmosphere and reduce the pressure and temperature of the particles to ambient conditions.
Conventional methods for depressurizing retorted oil shale particles have proven to be less than fully satisfactory. The use of mechanical devices such as lock vessels, solids flow control valves, and star feeders are expensive, complicated to operate, and prone to frequent failure through the rapid wearing of moving parts. In addition, such mechanical devices tend to produce an abundance of fines by the crushing and abrading of the particles. On the other hand, the use of non-mechanical hydrostatic devices leads to the undesirable liquid saturation of the particles. Such saturation causes operating problems which stem from the resultant loss of particle strength. More importantly, saturation may lead to retorted oil shale disposal problems. Retorted oil shale disposal is generally accomplished by using the particles as landfill. In constructing the landfill site, a degree of particle moisturization is desirable because such moisturization facilitates the requisite site compaction work. However particle moisturization to the point of saturation is undesirable because excess liquids will tend to gravitate out of the landfill site during the site's initial life. This devolution of landfill site material violates government regulations in many areas.
Conventional methods for cooling the retorted oil shale particles have also proven to be less than satisfactory. Such methods usually involve quenching the particles with water in such a way that the particles become undesirably liquid saturated and/or the produced steam is wasted into the atmosphere.
Accordingly, it is a major object of this invention to provide an apparatus and process for continuously removing retorted oil shale particles from a pressurized retort without resorting to mechanical sealing devices and/or hydrostatic seals.
It is a further object of this invention to provide an apparatus and process for cooling retorted oil shale particles without causing liquid saturation of the solid particles.
It is a further object of this invention to provide an apparatus and process for cooling retorted oil shale particles without having to use excessive quantities of water.
It is a further object of this invention to provide an apparatus and process for depressurizing and cooling retorted oil shale particles while avoiding particle degradation.
It is a still further object of this invention to provide an apparatus and process for imparting to retorted oil shale a controlled degree of moisturization.
These and other objects and advantages of the invention will become apparent to those skilled in the relevant art in view of the following description of the invention.